Release 3.5.1

Released September 27, 2026. Kafka share groups (KIP-932) are generally available, and kmq can update itself. The operator and the Helm chart are unchanged from 3.5.0.

Artifacts

Before you upgrade

• Kafka share groups: upgrade every server before share traffic resumes. This release adds new cluster commands for share groups, controlled by CONNECTORS_KAFKA_SHARE_FEATURE_VERSION (default 2). A server still on an older release stops when it meets one of them, and keeps stopping until it is upgraded; on a 3-server cluster this can cost the cluster its majority. Before a rolling upgrade, do one of these:

  • Stop share consumers and per-group configuration changes until every server runs 3.5.1, then upgrade normally.
  • Set CONNECTORS_KAFKA_SHARE_FEATURE_VERSION=1 on each server as you upgrade it, and raise it to 2, with a restart, once every server is upgraded. At 1, the new share-group features are unavailable: share groups cannot be deleted, per-group configuration writes and read_committed share groups are refused, and lock renewal is off.

  Downgrading is supported only if the setting stayed at 1 the whole time. Do not set share.isolation.level=read_committed until every server runs 3.5.1.

• New share groups start at the latest offset, as in Apache Kafka. Existing groups keep their position. To start new groups at the earliest offset, as before, set CONNECTORS_KAFKA_SHARE_AUTO_OFFSET_RESET=earliest.

• Share groups count against CONNECTORS_KAFKA_MAX_GROUPS, the limit that already applies to classic consumer groups. A share group counts until DeleteGroups removes it.

• Rolling restarts count a delivery attempt. Every share record in flight when a partition's leader changes counts one delivery attempt, including on each server restart of a rolling upgrade. Keep the per-group delivery limit at the default of 5 or higher.

Changes

• Kafka share groups are generally available, certified with the Java KafkaShareConsumer 4.3 and the Kafka 4.3 console tools on a single server and on 3-server clusters. See Share groups.
• Share-group administration: ListGroups with the type filter, DeleteGroups once no consumer is attached, per-group settings through kafka-configs.sh --entity-type groups, and read_committed share groups.
• Share-group monitoring: the kubemq_kafka_share_group_lag, kubemq_kafka_share_group_in_flight and kubemq_kafka_share_group_redelivered metrics, GET /api/kafka/share-groups, share groups on the dashboard's consumer-groups tab, and kmq kafka share-groups.
• Kafka fixes: a node that became the Kafka coordinator right after it became ready now loads the committed offsets, and a clustered topic-configuration reload that fails no longer serves empty settings or loses an acknowledged change.
• kmq updates itself. kmq update installs the latest kmq release, and kmq version --check reports whether a newer one exists. On Windows the update is scheduled rather than applied at once.

Known issues

• Images are published for linux/amd64 only. Release 3.5.2 adds linux/arm64.
• No default connector image is published. Set spec.image on every KubemqConnector.